Erythropoietin (Ep), is a glycoprotein hormone produced by the kidney and has been unequivocally proven to be the prime regulator of erythropoiesis in the adult mammalian species. Experiments have been designed to test in greater detail, the hypothesis that Ep produced by anemic lactating rats is transmitted to the newborn via the maternal milk and subsequently transported from the intestine to the circulation thereby stimulating erythropoiesis in these animals. Hyper transfused and normal neonatal rats will be used in these experiments. Milk and blood plasma from anemic lactating rats will be assayed for erythropoiesis stimulating activity. Detailed morphological studies of splenic and bone marrow erythroid cells in the neonate, as well as peripheral blood, will be made to assess the response of these cells to Ep. The effects of anti-Ep and neuraminidase, substance which inactivate Ep and decrease erythropoiesis in the adult rodent will be examined to test the hypothesis that in newborn rats regulation of red cell production differs, in some respects, from that observed in the adult. In addition to the studies with Ep, other experiments are planned with some hormones of the adenohypophyseal-target endocrine organ axis. These will include adenohypophyseal growth hormone (GH), adrenocorticotrophin (ACTH), triodothyronine (T3), testosterone, 5alpha-dihydrotestosterone and estradiol. Both parenteral and oral routes of administration will be included and both peripheral blood and blood-forming organs erythropoietic parameters (described above for Ep) will be utilized to determine the effectiveness of these hormones. These experiments will provide needed information on neonatal erythropoiesis. They will be followed by studies which cyclic nucleotides in which experiments are designed to examine the effects of cyclic adenosine - 3'5' - monophosphate on erythropoiesis in neonatal rats. Minority undergraduate students will participate in all phases of this project. They will receive a high degree of training in biomedical research (hematological techniques), executing experiments, analysis and interpretation of scientific data, and in writing and presenting scientific papers.